Too good to waste: How to recycle an old building for use on a brand new one

The protracted planning battle over the carbon emissions from the redevelopment of Marks & Spencer’s flagship Oxford Street store and the introduction of carbon offset pricing by Westminster council and the City of London has prompted a huge shift towards refurbishment over redevelopment in the capital over the past five years. And many in the industry – particularly large developers, designers, consultants and contractors – are keen to reduce the carbon emissions from construction.

But what about those buildings that are beyond viable refurbishment because they are in a terrible condition, or where the floor to ceiling heights are impossibly low? Sometimes, it may even be more carbon efficient to demolish a building rather than spend a lot of time and resources trying to bring a basket case up to scratch.

As a result, there is growing interest in finding ways to reduce the carbon footprint of new buildings, with developer GPE in the vanguard of this trend with the largest reclaimed steel project in the UK to date, which is currently onsite. The developer has set a target to be net zero by 2040, with an interim goal of reducing embodied carbon by 52% in just five years. Given the long lead time of large commercial projects, that means starting now.

30 Duke Street is situated in the heart of the West End across the street from Fortnum & Mason, with the north elevation fronting Piccadilly. It replaces two buildings, French Railways House and its neighbour on Jermyn Street.

We ended up developing the new-build proposals because the refurbishment options didn’t work given the bones of the building

Liam Bonnar, partner, Make Architects

Architect Liam Bonnar, a partner at Make, acknowledges these buildings were modernist icons but were too tired for refurbishment. He says the interiors had been hacked about and the building layout was compromised.

“With GPE, we looked at lots of different refurbishment options as well as a new-build scheme,” Bonnar explains. “Ultimately, we ended up developing the new-build proposals because the refurbishment options didn’t work given the bones of the building.”

Instead GPE has taken structural steel from a project that it is redeveloping in the City and reused this on 30 Duke Street. About 78% of the eight-storey, 106,000ft² building was constructed from reclaimed steel, saving 744 tonnes of carbon.

Carbon has also been saved by reusing the basement from the existing building. These savings are significant as most of the carbon saving from building refurbishment comes from reusing the structural frame.

Getting to this point has taken a lot of hard work and commitment from the project team. Initially the team found the carbon savings were not as great as hoped for after the stage three lifecycle carbon assessment. This prompted a big effort to identify further savings.

“We made a huge, collaborative effort where everyone wrote down carbon reduction opportunities for the project,” explains Louisa Treadwell, sustainability associate at Elliott Wood, the structural engineer and sustainability consultant on the project. “We identified whether these were easy wins and the stretch opportunities that would be a bit harder for us to implement.

“We then quantified the carbon for each of those different measures, and that was then given to the cost consultants. They provided a high level summary of whether these were cost neutral or involved a cost uplift or decrease.”

This exercise identified a carbon saving of 194 tonnes which, in a UK first, included a 30-tonne saving from using recycled glass and 82 tonnes by using recycled aluminum frames. These formed part of precast cladding panels which were made using substituting 50% of the cement content with GGBS.

This is the first project in London to deliver 100% recycled glass and also the first commercial project in the UK to deliver 100% recycled aluminum

Sal Capotosto, operations director, Mace

This is unusual for precast as GGBS lengthens the initial curing time, reducing the output of the mould. For Mace operations director Sal Capotosto these panels epitomised the ethos of this project.

“The panels represent the perfect balance and blend between off-site productivity, carbon reduction and circular economy. The panels were prefabricated offsite, which reduces carbon in terms of manufacturing, transport and improved productivity on site. This is also the first project in London to deliver 100% recycled glass and also the first commercial project in the UK to deliver 100% recycled aluminum,” he says.

Capotosto adds that this was only possible thanks to close collaboration and early engagement with the project team, as called for by the private sector playbook which is being used on this project. “Because of that early engagement, we were able to design and manufacture the panels well in advance,” he says.

“80% of the panels required for the job were built six weeks before the steel frame completed. That is the value of early engagement.”

The panels also incorporated Portland stone reclaimed from the previous building. This made up 17% of the total needed, saving 62 tonnes of new stone.

The reason why this project incorporates such a high percentage of reclaimed steel is thanks to GPE and Elliott Wood taking the decision in 2019 to recover 1,500 tonnes of structural steelwork from the demolition of a 10-storey office building called City Place House in Aldermanbury Square. This was done in partnership with specialist EMR metal recycling who assessed, tested and categorised the steel before storing for later use.

Approximately 375 tonnes of that steel was used at Duke Street. “The rest of the steel was left with with EMR, either for future GPE projects or for recycling to the wider market,” Capotosto says.

Treadwell says 30 Duke Street was not specifically designed around the availability of the sections of reclaimed steel from City Place House because the testing process had not been completed. The building was designed around the sections that initial inspection suggested were useable – but this changed after testing.

“There were several instances throughout stage three, and at the beginning of stage four, where the steel reuse numbers were changing because the steel went through a two-stage testing process,” explains Treadwell. “Some of the steel sections had to come out when the second test happened, which meant we had to find some other sections.

“This meant that, quite often, some of the sections had to be moved around the building structure. It was a long process and quite time-intensive for our engineers.”

This process prompted the team to move from manually measuring the steel section tolerances to a digital tool, which was more accurate and reduced the number of sections that had to be moved around.

Flexibility was key here. For example, some loads are being taken by two small beams rather than one section. City Place House featured long spans which meant the columns had the capacity to enable 14m spans between the core and building perimeter at 30 Duke Street.

Elliott Wood structural engineer Gemima Walker acknowledges that these columns are quite large sections, but says these are working efficiently. “The grade the steel ended up being after testing was S275 [lower strength] rather than S355,” she explains. “If we had done it out of new steel, we would have used S355 and the sections could have been smaller.

“Because we were using reclaimed steel, it was a lower grade after testing. But it turned out that they were actually used quite efficiently in the end.”

A third of the steel used for 30 Duke Street had to come from sources other than City Place House. About 11.5% was reclaimed steel from EMR and Cleveland Steel’s own stock, while 22.5% was new steel, which included 10% for new sections that could not be sourced from the reclaimed steel.

“There has to be a point where you stop looking to the wider market, and also the types of and sizes of steel that was needed in the building just wasn’t available,” Treadwell explains. These tend to be smaller pieces of steel that are more likely to be damaged during deconstruction, she adds.

The remaining 11.5% of steel consists of connection plates. Walker says reclaimed steel connecting plates would need to be made by cutting these out of the web of some of the recovered beams. “We did have discussions with the steel fabricator about the feasibility of this, and it sounded as though it could be done, but it would be quite time-consuming and costly,” she says.

The project was the first in London to use Saint-Gobain’s Glass Forever Scheme, a closed loop recycling scheme. Twelve tonnes of glass from the old building were removed from the window frames, cleaned, broken up and bagged for collection by Saint-Gobain for recycling into its Orae glass product.

Saint Gobain says that Orae is made from a minimum of 70% recycled cullet and has a carbon footprint just 42% of its standard clear glass.

Similarly, the aluminium window frames were collected in skips, taken away, melted down and extruded into new sections. All the new windows on the project are made from Hydro Circal 100R, a 100% recycled aluminium product, which saved another 82 tonnes of carbon.

The only disadvantage of using recycled aluminium is that it cannot be anodised. It has to be painted instead.

Capotosto says there was a limit to how much of the original Portland stone could be reused as some was not reusable because of how it was fixed to the original building, and because of quality issues. The stone had to be thick enough so that it could be sliced down the middle to present a new face to the street.

The reclaimed Portland stone on the facade can be easily identified as this initially suffers from efflorescence. Bonnar says this should disappear after a few months. All 3.6 tonnes of the granite from the original building has been reused too.

Another big carbon saving of 250 tonnes comes from using reclaimed raised access floor tiles. Some of these were reclaimed from the building formerly on the site, but most come from 10 Upper Bank Street at Canary Wharf, which has undergone an internal reorganisation.

After trialling material passports at another Mace project, Edenica in the City, these have been employed at 30 Duke Street for the steelwork, concrete, precast facade panels and windows. Mace is also trialling the measurement of the carbon impacts of MEP equipment due to a lack of data on these elements.

Have these initiatives added to the cost of the project? Capotosto says that, as GPE was in the fortunate position of having a donor building, the cost increase over new steel once the reclaimed steel had been removed, cleaned and tested was “negligible”, although this would not have been the case if reclaimed steel had to be procured on the open market. Deconstructing the donor building was more expensive than simple demolition as more care and time is needed to take the building apart.

Reclaiming the stone, recycling the glass and procuring the reclaimed access flooring did not come with a cost premium, although the recycled aluminium was slightly more expensive. But this minor cost increase pales into insignificance given the considerable carbon savings – and in time could disappear, especially once a market for reclaimed structural steel is established.

30 Duke Street is due to complete next August, and GPE has secured a pre-let for the whole building to investment firm CD&R. Did the focus on the circular economy help to clinch the deal?

“The location is a big driver, and the fact the floors are column free has been a huge selling point,” explains Franke Blande, the sustainability lead for GPE. “The sustainability aspects were part of it, but not the main driver. However it definitely helped push it over the edge.”

And the lessons learnt from this project will be invaluable for saving embodied carbon on future projects in cases where the refurbishing of an existing building is neither  viable nor practical.